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Confined Space. An Overview of OSHA Standards and Confined Space Hazards. Developed by Western Iowa Tech Community College

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Confined space

Confined Space

An Overview of OSHA Standards and Confined Space Hazards

Developed by Western Iowa Tech Community College

This material was produced under a grant (SH-16634-07-60-F-19) from the Occupational Safety and Health Administration, U.S. Department of Labor. It does not necessarily reflect the views or policies of the U.S. Department of Labor, nor does the mention or trade names, commercial products, or organization imply endorsement by the U.S. government.

Confined space entry

Confined Space Entry

Construction Industry Standard 1926.21(b)(6)

General Industry Standard 1910.146

Best Practices for all Industries

Confined space1
Confined Space

All employees required to enter into confined or enclosed spaces shall be instructed as to the nature of the hazards involved, the necessary precautions to be taken, and in the use of protective and emergency equipment required. The employer shall comply with any specific regulations that apply to work in dangerous or potentially dangerous areas.

Typical confined spaces
Typical Confined Spaces

  • Boiler, Degreaser, Furnace

  • Pipeline, Pit, Pumping Station

  • Reaction or Process Vessel, Mills

  • Septic Tank, Sewage Digestor

  • Silo, Storage Tank, Barges

  • Sewer, Utility Vault, Manhole

  • Trenches, Shafts, Caissons

How to identify confined spaces
How to Identify Confined Spaces

  • Limited Openings for Entry and Exit

  • Unfavorable Natural Ventilation

  • Not Designed for Continuous Worker Occupancy

Categorizing work space
Categorizing Work Space

* Space large enough to enter &;

* Limited or Restricted entry or exit &;

* Not designed for continuous worker



Not a confined Space


Confined Space









Hazardous Atmosphere


Engulfment Hazard




Configuration Hazard


Any other recognized

serious hazard

Limited openings for entry exit
Limited Openings for Entry/Exit

  • Openings as small as 18 inches in diameter.

  • Difficult to enter with SCBA or other life-saving equipment.

  • Difficult to remove downed worker in folded up or bent over position.

  • Exit from large openings may be difficult due to presence of ladders, hoists, etc.

Unfavorable natural ventilation
Unfavorable Natural Ventilation

  • Lack of air movement in and out of the space can create an atmosphere much different than the outside atmosphere.

  • Deadly gases can be trapped inside.

  • Organic materials can decompose.

  • May not be enough oxygen due to presence of other gases or chemical reactions such as rusting.

Not designed for continuous worker occupancy
Not Designed for Continuous Worker Occupancy

  • Most confined spaces are not designed to enter and work in on a regular basis.

  • Designed to store a product.

  • Enclose materials or processes.

  • Transport products or substances.

  • Occasional worker entry for inspection, repair, cleanup, maintenance, etc.

Dangerous combinations
Dangerous Combinations

  • Presence of all three confined space characteristics can complicate the situation.

  • Working in and around the space.

  • Rescue operations during emergencies.

  • Worsened conditions due to work activities:

    • Welding and cutting, use of bonding agents

    • Cleaning with solvents, use of other chemicals

    • Use of gas-powered equipment

Hazards of confined spaces
Hazards of Confined Spaces

  • Oxygen Deficient Atmospheres

  • Oxygen Enriched Atmospheres

  • Flammable Atmospheres

  • Toxic Atmospheres

  • Temperature Extremes

  • Engulfment Hazards

  • Noise, Slick/Wet Surfaces, Falling Objects

  • Mechanical Hazards

Hazardous atmosphere definitions
Hazardous Atmosphere Definitions

“Hazardous atmosphere” means an atmosphere that may expose employees to the risk of death, incapacitation, impairment of ability to self-rescue (that is, escape unaided from a permit space)injury, or acute illness from one or more of the following causes:

(1) Flammable gas, vapor, or mist in excess of 10percent of its lower flammable limit (LFL);

Hazardous atmosphere definitions1
Hazardous Atmosphere Definitions

“Hazardous atmosphere” (cont’d)

(2) Airborne combustible dust at a concentration that meets or exceeds its LFL; NOTE: This concentration may be approximated as a condition in which the dust obscures vision at a distance of 5 feet or less.

(3) Atmospheric oxygen concentration below 19.5 percent or above 23.5 percent;

Hazardous atmosphere definitions2
Hazardous Atmosphere Definitions

“Hazardous atmosphere” (cont’d)

(4) Atmospheric concentration of any substance for which a dose or a permissible exposure limit is published in Subpart G, Occupational Health and Environmental Control, or in Subpart Z, Toxic and Hazardous Substance , of this Part which could result in employee exposure in excess of its dose or permissible exposure limit.

(5) Any other atmospheric condition that is immediately dangerous to life and health.

Oxygen deficient atmospheres
Oxygen Deficient Atmospheres

19.5 % Minimum acceptable oxygen level.

15 - 19% Decreased ability to work strenuously. Impair coordination. Early symptoms.

12-14% Respiration increases. Poor judgment.

10-12% Respiration increases. Lips blue.

8-10% Mental failure. Fainting. Nausea Unconsciousness. Vomiting.

6-8% 8 minutes - fatal, 6 minutes - 50% fatal 4-5 minutes - possible recovery.

4-6% Coma in 40 seconds. Death

Oxygen enriched atmospheres
Oxygen Enriched Atmospheres

  • Oxygen level above 21%.

  • Causes flammable and combustible materials to burn violently when ignited.

  • Hair, clothing, materials, etc.

  • Oil soaked clothing and materials.

  • Never use pure oxygen to ventilate.

  • Never store or place compressed tanks in a confined space.

Flammable atmospheres
Flammable Atmospheres

  • Critical Factors:

    • Oxygen content in the air.

    • Presence of a flammable gas, or vapor

    • Presence of dust (visibility of 5’ or less)

  • Proper air/gas mixture can lead to explosion

  • Typical Ignition Sources:

    • Sparking or electric tool.

    • Welding / cutting operations.

    • Smoking

Toxic atmospheres
Toxic Atmospheres

  • Product stored in a confined space:

    • Gases released when cleaning.

    • Materials absorbed into walls of confined space.

    • Decomposition of materials in the confined space.

  • Work performed in a confined space:

    • Welding, cutting, brazing, soldering.

    • Painting, scraping, sanding, degreasing.

    • Sealing, bonding, melting.

  • Areas adjacent to a confined space.

    • Exhaust , pumps, generators

  • Hydrogen sulfide
    Hydrogen Sulfide

    • Decomposition of materials. Human waste.

    • Rotten egg odor at low concentrations.

    • Possibly no warning at high concentrations.


      10 ppm Permissible Exposure Level 8 Hours

      50 - 100 Mild Irritation - eyes, throat 1 Hour

      200 - 300 Significant Irritation 1 Hour

      500 -700 Unconsciousness, Death 1/2 - 1 Hour

      >1000 Unconsciousness, Death Minutes

    Confined space

    Carbon Monoxide

    • Odorless, Colorless Gas.

    • Combustion By-Product.

    • Quickly collapse at high concentrations.

    • PPMEffectTime

    • 50 Permissible Exposure Level 8 Hours

    • 200 Slight headache, discomfort 3 Hours

    • 600 Headache, discomfort 1 Hour

    • 1000-2000 Confusion, nausea, headache 2 Hours

    • 1000-2000 Tendency to stagger 1 1/2 Hours

    • 1000-2000 Slight heart palpitation 30 Min.

    • 2000-2500 Unconsciousness 30 Min.

    Temperature extremes
    Temperature Extremes

    • Extremely hot or cold temperatures.

    • Steam cleaning of confined spaces.

    • Humidity factors.

    • Extremely cold liquids.

    • Work processes inside the confined space can increase temperature extremes.

    • Personal protective equipment.

    Engulfment hazards
    Engulfment Hazards

    • Loose, granular materials stored in bins and hoppers - grain, sand, coal, etc.

    • Crusting and bridging below a worker.

    • Flooding of confined space.

    • Water or sewage flow.

    Other hazards
    Other Hazards

    • Noise

      • Amplified due to acoustics within the space.

      • Damaged hearing, affect communication.

  • Slick / Wet Surfaces

    • Slips and falls.

    • Increased chance of electric shock.

  • Falling Objects

    • Topside openings expose workers inside confined space to falling objects.

    • Mechanical

    • Drive Shafts

    • Drive Gears

  • Testing the atmosphere
    Testing The Atmosphere

    • Verify presence of safe work atmosphere.

    • Test all areas of a confined space.

      • Top, Middle, Bottom, and each end

    • Methane is lighter than air.

    • Carbon Monoxide is the same as air.

    • Hydrogen Sulfide is heavier than air.

    • Oxygen Deficiency.


    • First option to correct problems.

    • Must be aware of hazards you are trying to correct in the confined space.

    • Air intake in a safe location to draw fresh air only.

    • Continuous ventilation whenever possible.

    • Retest the confined space before entry.


    • Locking and tagging out electrical sources.

    • Blanking and bleeding pneumatic and hydraulic lines.

    • Disconnecting mechanical drives and shafts.

    • Securing mechanical parts.

    • Blanking sewer and water flow.

    • Locking and tagging out shutoff valves.


    • Air-Purifying Respirators

      • Filter dangerous substances from the air.

      • Must know the type and amount of hazardous substance present in the confined space.

      • NEVER use with oxygen deficiency!

    • Air-Supplying Respirators

      • Deliver a safe supply of breathing air from a tank or an uncontaminated area nearby.

      • Must be adequately monitored.

    Standby rescue
    Standby / Rescue

    • Worker assigned to remain outside the confined space and be in constant contact with the workers inside.

    • Know emergency rescue procedures.

    • 50% of workers who die in confined spaces are would-be rescuers.

    • Trained in use of emergency rescue equipment and PPE.

    Permit entry systems
    Permit Entry Systems

    • Written permit signed by entry supervisor.

    • Verifies pre-entry precautions have been taken and the space is safe to enter.

    • Posted at entry to confined space.

    • Specifies apparent hazards and corrective actions taken prior to entry.

    • Requires termination of permit when task is completed or when new conditions exist.

    Entry permit requirements
    Entry Permit Requirements

    • Date, location, and name of confined space.

    • Purpose of entry and known hazards.

    • Duration of entry permit time.

    • Authorized entrants, attendants, supervisors.

    • Air testing results - signature of tester.

    • Protective measures to be taken.

      • Ventilation, Isolation, Flushing

      • Lockout / Tagout, Purging

    Entry permit requirements1
    Entry Permit Requirements

    • Name and phone numbers of rescue and emergency services.

    • Communication procedures.

    • Special equipment and procedures.

      • Personal protective equipment.

      • Alarm procedures.

      • Rescue equipment.

      • Respirators.

    Training and education
    Training and Education

    • All workers who must enter confined spaces

    • All attendants and rescue team members.

    • Prior to initial work assignment.

    • Retraining:

      • Job duties change.

      • Change in permit-space program.

      • New hazards are present.

      • Job performance indicates deficiencies.


    • Definition of a confined space

    • Hazards of a confined space

    • Neutralizing hazards in a confined space

    • Steps for proper confined space entry

    • Proper permits for confined space entry

    • Other related issues of confined spaces

    Confined spaces
    Confined Spaces

    Questions or Comments?